The present invention relates to a method and an arrangement determining where to position fixating means for hip fractures and an arrangement for providing attachment of said fixating means controlled by data from said method.
Present methods regarding, for example, hip fracture surgery involves a great deal of craftsmanship. A patient with an injured leg is placed supine on a fracture table and a reduction maneuver is carried out. The foot of an injured leg is firmly fixed in a specially built shoe. Traction and rotation are applied until the fracture is reduced.
A fixation of an injured leg is normally so firm that no movement will take place unless a substantial force is applied to the leg. A mobile X-ray apparatus, a xe2x80x9cC-armxe2x80x9d, with two perpendicular radiographs, the anteroposterior (AP) and the lateral (Lat) projections, checks quality of reduction. The result of a reduction can only be judged through said at least two radiographs, and no correction for variations in hip rotation is possible.
Screws are inserted in order to fixate the fractured bone parts. The screws are introduced by a hand-held drill which opens up guide holes for the screws, whereby a surgeon has to judge the position of the drill from said two perpendicular radiographs and manually adjust the position of the drill in three dimensions, which is a very difficult task.
Unfortunately, the insertion of screws very often has to be repeated. Repeated trials of insertion destroy the bone structure in the femoral neck.
To be able to check the quality after a performed hip fracture surgery a method was developed for determining the post surgery position of a fixating means. It was introduced by the inventor of the present invention in his thesis xe2x80x9cInternal Fixation of Femoral Neck Fracturesxe2x80x9d, Stockholm 1993, ISBN 91-628-0804-4. Nevertheless, the method has only been used for post-surgery quality checks and scientific statistics, and it has not occurred to or been obvious to any person skilled in the art to modify the method so it can be used in determining how and where to drill in a femoral bone fracture in order to attach fixating means and facilitate healing of said fracture in a best possible way.
Today, orthopedic surgery has promulgated towards sophisticated hi-tech implants being manually inserted through in-precise techniques. To manually insert implants is a task for a highly skilled orthopedic surgeon with, for example, 10 years of training in the present medical field.
For diagnosis groups, where a great number of injuries is accumulated, the result of performed surgery is less satisfactory than it could be. Hip fractures belong to such a group, whereby about 18,000 incidents/year occur in Sweden alone, 9,000 cervical and 9,000 pertrochanteric, to a cost of approximately SEK 1.4 billions.
Despite of the more than 100 different fixating methods developed for this kind of fractures, the result of performed surgery is relatively poor. As much as approximately 35% of all cervical fractures do not heal, and 20% of them have to be re-operated within a time period of 1-2 years. For pertrochanteric fractures the same rates are 10% and 4% respectively. Every re-surgery approximately costs SEK 185,000.
It is agreed with among surgeons and other experts that the main reason for the high percentage of re-surgery is an inadequately positioning of the fixating screws, which hold the fracture together during the following healing process, see xe2x80x9cFixation of femoral neck fractures: comparison of the Uppsala and Von Bahr screws.xe2x80x9d By Rehnberg and Olerud, Acta Orthop Scand 60, 1989, p. 579-584.
Considering the costs of SEK 185,000 for one re-surgery, a decrease in the rate of such surgery with 50% would gain a save of SEK 160 millions a year in surgery costs. A bigger Swedish Hospital would save approximately SEK 8 millions, not to say what is gained in relief for fractured patients.
A known arrangement to support surgery is the so-called ROBODOC(copyright) Surgical Assistant System. The ROBODOC(copyright) robot is able to precisely prepare a femoral channel for placement of a cementless prosthesis.
Due to the manual surgery technique involved in surgery relating to bone fractures and judgements made from said radiographs in real time during surgery/surgical treatment without any tools for performing analysis, the X-ray radiation will be unnecessary high for patients and personnel serving during surgery.
It would be an advantage therefore, to provide a method and an arrangement that can aid a surgeon in preparing and supporting orthopedic surgery. Such a method and arrangement are set forth through attached independent claims. Specific embodiments of the invention are introduced through the attached dependent claims. Hence the method and arrangement of the present invention and details thereof provides such advantages.
The present invention generally relates to a method used for determining where to position fixating means or fixation devices in a hip fracture and an arrangement used to aid surgeons. It is controlled by data from said method. Said method brings about data out of conventional radiographs taken to detect fractures. Hence, the method is applied after diagnosis and before any medical treatment has taken place.
Accordingly, the present invention provides a method for determining, in three dimensions, where to position fixating means in a hip fracture by pre-surgery analysis of at least one anteroposterior and one lateral digitized radiograph of said fracture. It comprises the following steps:
determining a construed femoral shaft axis out off said graphs from at least two midpoints on said shaft axis and drawing a line through said midpoints;
determining a construed femoral neck axis from at least two midpoints on said neck axis and drawing a line through said midpoints;
determining femoral neck angles;
determining a femoral head diameter out off said graphs by placing a circle over the perimeter of the femoral head;
determining a femoral neck diameter out off said radiographs by drawing a line, perpendicular to the femoral neck axis, at the intersection of the femoral head sphere and the central femoral neck axis;
scaling and rotating said radiographs to a predefined size and position, using an angle between the femoral shaft and an Y-axis in said digitized radiographs, and said diameter of the femoral head in both the AP and Lat projections;
determining the distance from said neck axis and the center of said femoral head perpendicular to the femoral neck-axis, representing a remaining displacement of the hip fracture which is implicitly known from said head diameter;
determining the height of a medial cortex out off the anteroposterior graph; displaying said femoral neck angles;
constructing and displaying cross-sections of the femoral head and neck with a predetermined degree of accuracy,
rotating said cross-sections of the femoral head and neck in order to determine a degree of derotation of the hip, imposed by the fracture,
displaying the degree of hip rotation in said anteroposterior and lateral radiographs; and
using said steps in an arrangement in order to determine a position, in three dimensions for attachment of said fixating means and to pre-adjust a tool to work in said position.
In one embodiment, femoral neck angels are displayed as lines and numerical values i said digitized graphs, said lines are automatically re-drawn if the value is changed.
Another embodiment comprises that symbols for said fixating means are placed within the cross-section of the femoral neck.
A still further embodiment includes a warning function, which is activated if said fixating means are placed outside the head or neck in said digitized radiographs.
Fixating means for attachment are automatically displayed in said cross-sections with relation to made measurements according to one embodiment of the present invention.
A still further embodiment provides means for putting down symbols for fixating means in the digitized radiographs.
Yet another embodiment of the present invention comprises that said lines are regression lines drawn from at least three midpoints.
The arrangement according to the present invention provides for attachment of fixating means in a hip fracture, through analyzing at least one anteroposterior and one lateral digitized radiographs of said fracture. It comprises:
a measurement means for determining the femoral shaft axis out off said graphs from at least two midpoints on said shaft axis, and drawing a line through said midpoints;
a measurement means for determining the femoral neck axis from at least two midpoints on said neck axis and drawing a line through said midpoints;
a measurement means for determining femoral neck angels;
a measurement means for determining a femoral head diameter out off said graphs by placing a circle over the perimeter of said femoral head;
a measurement means for determining a femoral neck diameter out off said radiographs by drawing a line, perpendicular to the femoral neck axis, at the intersection of a femoral head sphere and a central femoral neck axis;
a driver means or function for scaling and rotating said radiographs to a predefined size and position, using an angle between the femoral shaft and an Y-axis in said digitized radiographs, and said diameter of the femoral head in both the AP and Lat projections;
a measurement means for determining the distance from the femoral neck axis to the center of said femoral head perpendicular to the femoral neck-axis, representing a remaining displacement of the fracture, which is implicitly known from said femoral head diameter;
a measurement means for measuring the height of the medial cortex out off said anteroposterior radiographs;
a display means for displaying said neck angles;
a display means for providing displays of cross-sections of said femoral head and femoral neck with a predetermined degree of accuracy,
a driver means or function for rotating said cross-sections of the femoral head and neck in order to determine a degree of hip derotation between said head and neck, imposed by the fracture;
a display means for displaying said hip rotation in said anteroposterior and lateral radiographs; said means
providing control input to a robot with tool means on said robot for working in a direction given by said control input, and distortion correcting means compensating for x-ray distortion.
In one embodiment, the femoral neck angels are displayed, by said means for displaying, as lines and numerical values in said digitized graphs, said lines are automatically redrawn by graphic means if the value is changed.
Another embodiment includes that symbols for said fixating means are placed within the cross-section of the femoral neck and displayed by said means for displaying.
A further embodiment activates a warning function if said fixating means are placed outside of the femoral head or neck in said digitized radiographs.
A still further embodiment includes that fixating means for attachment is automatically displayed in said graphs with relation to made measurements.
Means are provided for putting down symbols for fixating means in the digitized radiographs in one embodiment of the present invention.
Yet another embodiment of the present arrangement comprises that said lines are regression lines drawn from at least three midpoints.